Department of Psychiatry, Institute of Psychiatry, Kings College London, UK and Second Department of Psychiatry, Attikon General Hospital, National and Kapodistrian University of Athens Medical School, Athens, Greece
Section of Neuroscience and Emotion, Department of Psychiatry, Institute of Psychiatry, Kings College London
Department of Psychiatry, Institute of Psychiatry, Kings College London
Brain Image Analysis Unit, Institute of Psychiatry, Kings College London
Department of Psychiatry, Institute of Psychiatry, Kings College London
Department of Psychiatry, Institute of Psychiatry, Kings College London, and Wellcome Department of Imaging Neuroscience, Institute of Neurology, University College London, London, UK
Correspondence: Dr Panayiota G. Michalopoulou, Box PO 67, Institute of Psychiatry, De Crespigny Park, London SE5 8AF, UK. Email: spdppam{at}iop.kcl.ac.uk
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The recognition of negative facial affect is impaired in people with schizophrenia. The neural underpinnings of this deficit and its relationship to the symptoms of psychosis are still unclear.
Aims
To examine the association between positive and negative psychotic symptoms and activation within the amygdala and extrastriate visual regions of patients with schizophrenia during fearful and neutral facial expression processing.
Method
Functional magnetic resonance imaging was used to measure neural responses to neutral and fearful facial expressions in 11 patients with schizophrenia and 9 healthy volunteers during an implicit emotional task.
Results
No association between amygdala activation and positive symptoms was found; the activation within the left superior temporal gyrus was negatively associated with the negative symptoms of the patients.
Conclusions
Our results indicate an association between impaired extrastriate visual processing of facial fear and negative symptoms, which may underlie the previously reported difficulties of patients with negative symptoms in the recognition of facial fear.
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Nine healthy dextral individuals (five men, four women) comparable for age and years of education were recruited as a comparison group from the local population. Exclusion criteria for all participants were illicit substance or alcohol misuse within the past 2 years, a history of neurological illness, head injury or other significant medical illness. All participants had normal pre-morbid IQ scores, estimated with the National Adult Reading Test;13 control group participants had significantly higher scores (t=3.49, d.f.=18, two-tailed P=0.003). Written informed consent was obtained for all participants and the study was approved by the Institute of Psychiatry research ethics committee.
Imaging study
Procedure
The participants took part in an event-related fMRI experiment while
viewing grey-scale images depicting prototypical facial expressions of fear
and sadness, a neutral facial expression and a fixation cross. The facial
stimuli were from the standard set of prototypical facial expressions of the
six basic emotions by Ekman &
Friesen.14 The
sad face processing data are not discussed in this paper.
The sequence of the four stimuli (fearful face/sad face/neutral face/fixation cross) was randomised and common to all participants. Twenty stimuli were presented per condition, depicting either a face or the fixation cross, each presented for 3 s with an inter-stimulus interval of 6 s, and the duration of the experiment was 8 min. This was an implicit emotional processing task, with participants indicating the gender of the face by moving a joystick. No response was required to the fixation cross.
Data acquisition and image analysis
Data were acquired using a 1.5 T scanner at the Maudsley Hospital, London,
and analysed with software developed at the Institute of Psychiatry, London,
using a standard non-parametric approach. Whole-brain analysis of variance was
used to estimate significant within-group and between-group effects. A
detailed description of the data acquisition and image analysis is available
as a data supplement to the online version of this paper. A correlational
analysis was used to examine associations between PANSS positive and negative
sub-scale scores and activation within the brain regions specified in our
a priori hypotheses: the fusiform gyrus, the superior temporal gyrus
and the amygdala.
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View this table: [in a new window] | Table 1 Demographic and clinical characteristics of the sample |
Behavioural results
There was no significant difference in performance between the patient and
control groups in the gender discrimination task (Mann–Whitney
U=38.0, z=–0.90, two-tailed P=0.37 for
fearful expression; Mann–Whitney U=37.5,
z=–0.94, P=0.35 for neutral facial expression).
Imaging results
Within-group comparisons
The whole-brain analysis of variance (ANOVA) revealed the following
within-group significant differences:
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View this table: [in a new window] | Table 2 Clusters showing significant activation differences to fearful v. neutral faces in healthy participants and patients |
![]() View larger version (40K): [in a new window] [as a PowerPoint slide] |
Fig. 1 Coronal view of the brain showing right fusiform gyrus responses to fearful
v. neutral faces (a) in the control group (x=32,
y=–74, z=–13) and (b) the between-group
differences, where control participants demonstrated greater activation than
the participants with schizophrenia (x=25, y=–77,
z=–13). R, right hemisphere; L, left hemisphere.
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![]() View larger version (41K): [in a new window] [as a PowerPoint slide] |
Fig. 2 Sagittal view of the brain showing right amygdala responses to fearful
v. neutral faces (a) in the control group (x=25,
y=–7, z=–7) and (b) the between-group
differences, where control participants demonstrated greater activation than
participants with schizophrenia (x=22, y=–7,
z=–13).
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Between-group comparisons
The whole-brain ANOVA revealed the following between-group significant
differences:
Correlational analyses
Correlational analyses in the patient group revealed a significant negative
correlation between the PANSS negative sub-scale score and activation within
the left superior temporal gyrus during the processing of fearful faces
(Pearson r=–0.84, P=0.001; Spearmans
rho=–0.74, P=0.01) (Fig.
3). This correlation remained significant after controlling for
the patients IQ (r=–0.805, d.f.=9, P=0.005) and
gender (r=–0.847, d.f.=9, P=0.002). No other
correlation between measured brain activity and PANSS scores was statistically
significant.
![]() View larger version (12K): [in a new window] [as a PowerPoint slide] |
Fig. 3 Sagittal view of the brain showing between-group differences in neural
response of left superior temporal gyrus to fearful faces, where control
participants demonstrated greater responses than participants with
schizophrenia (x=–47, y=–22, z=9). The
graph shows the correlation between the Positive and Negative Syndrome Scale
(PANSS) negative sub-scale scores and the mean blood oxygen level dependent
(BOLD) signal change in the left superior temporal gyrus of participants with
schizophrenia (Pearson r=–0.84, P=0.001;
Spearmans rho=–0.74, P=0.01).
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Healthy participants demonstrated greater activation within the right fusiform gyrus and superior temporal gyrus in response to fearful compared with neutral faces. This finding supports enhancement of extrastriate visual cortices activation by emotionally salient stimuli.5,6 In contrast, participants with schizophrenia showed significantly reduced activation within these regions during facial fear processing compared with healthy controls. This is consistent with earlier findings,19–21 and may reflect a deficit in the visual processing of facial fear in people with schizophrenia.
Participants with schizophrenia demonstrated a left lateralised reduction in superior temporal gyrus activation, similar to the findings of Johnston et al.22 The left lateralised reduction in superior temporal gyrus activation in our study may represent some reversal of the normal right lateralised temporal lobe response to facial fear in people with schizophrenia and may be indicative of impaired function of the left superior temporal gyrus during fear processing in schizophrenia. This might reflect a more general emotional deficit, as an abnormal left lateralised temporal lobe activation has been previously demonstrated in response to emotional prosody.23
The cortex surrounding the superior temporal sulcus, along with the fusiform gyrus, is associated with social cognition. Specifically, these regions are involved in the visual perception of socially relevant stimuli.24 Findings from neuroimaging, electrophysiological and single-cell recording studies have associated the visual perception of biologically salient motion with the activation of the posterior aspects of the superior temporal sulcus and the adjacent superior temporal gyrus.25,26 The perception of the changeable aspects of the faces such as facial emotion, gaze direction and lip movements also elicits activation within the superior temporal sulcus and the adjacent superior temporal gyrus, even in response to implied motion evidenced by static visual stimuli, such as facial expressions.25 A deficit in biological motion perception may result in deficient social perception, and cognition and social functioning. People with schizophrenia and severe negative symptoms exhibit a pronounced difficulty in the recognition of facial emotions,4 particularly facial fear.2,27 They also exhibit impairments in social cognition tasks such as theory of mind tasks, also associated with negative symptoms.28–30 The social cognition deficits may contribute to the social functioning deficits of the patients with negative symptoms.31
The cortical processing of motion-related visual stimuli is impaired in people with schizophrenia and this impairment is more intense in those with severe negative symptoms.9 This deficit has been associated with the middle temporal cortical visual area, which responds to both scrambled motion and biological motion sequences. The association of activation of the superior temporal cortex, which responds selectively to all aspects of biological motion, with negative symptoms has not been investigated. Consistent with our hypothesis, the severity of negative symptoms of the participants with schizophrenia correlated negatively with the degree of activation attenuation within the left posterior superior temporal gyrus. Our finding indicates an association between impaired extrastriate cortical visual processing of facial fear and negative symptoms in people with schizophrenia. This association may underlie the previously reported pronounced difficulties of patients with high levels of negative symptoms in the recognition of fearful faces.
The neural response within the right fusiform gyrus in the participants with schizophrenia in our study did not correlate with the severity of negative symptoms. This is at odds with an earlier PET study,8 which showed decreased glucose metabolic rate in the right fusiform area of patients with predominantly negative symptoms and a negative correlation with the negative symptoms of the patients. The finding of Potkin et al8 was regarded as consistent with the difficulties of the patients with negative symptoms in identifying the emotional content of faces and scenes. The differences in these results may be secondary to the different time frames between event-related fMRI and PET, as the occipital cortices are associated with early visual processing.
Deficits in visual tasks in the participants with schizophrenia could be attributed to their attentional deficits, which could lead to lower engagement with the task during the scanning session. However, the findings of our study are not likely to derive from the patients attentional impairments, since their performance in the gender discrimination task did not differ significantly from the control groups performance.
Methodological considerations
There are several potential limitations to this study. First is the issue
of generalisability of these results from the analysis of a relatively small
number of participants. A non-parametric statistical approach to the analysis
of the imaging data is preferred, and we have used stringent thresholds for
all of our analyses to minimise any type I errors; the significance threshold
was set to give less than one false-positive cluster over the whole brain.
This would suggest that our findings are relatively robust. Second,
participant characteristics–including symptoms and medication in the
patient group–may also influence the between-group variability. Ideally,
we would have recruited unmedicated patients for this study; however,
pragmatically these were difficult to ascertain. Examining for medication
effects within the patient group, we found no significant correlation between
the medication dose and the blood oxygen dependent level response values
within the right amygdala, right fusiform gyrus and left superior temporal
gyrus. Similar findings have also been demonstrated in unmedicated
patients.21 One
possibility is that activation differences between patients and controls are
secondary to differences in performance. The gender discrimination task we
used placed minimal performance demands on the
participants,32
thereby reducing the possibility that performance differences might confound
our results.
In summary, we have confirmed that patients with schizophrenia demonstrated reduced neural responses within extrastriate visual cortices and amygdala during processing of facial fear. A left lateralised reduction of superior temporal gyrus activity correlated with increasing severity of negative symptoms. This association may underlie the previously reported pronounced difficulties of people with schizophrenia and high levels of negative symptoms in the recognition of fearful faces.
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P. J. Johnston, P. G. Enticott, A. K. Mayes, K. E. Hoy, S. E. Herring, and P. B. Fitzgerald Symptom Correlates of Static and Dynamic Facial Affect Processing in Schizophrenia: Evidence of a Double Dissociation? Schizophr Bull, October 26, 2008; (2008) sbn136v1. [Abstract] [Full Text] [PDF] |
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